Magnetization and Specific Absorption Rate Studies of Ball-Milled Iron Oxide Nanoparticles for Biomedicine

Table 2

Mössbauer hyperfine parameters for γ-Fe₂O₃ nanoparticles measured at RT.

Sample	Particle diameter (nm)	Spectral component	δ (mm/s)	Δ𝐸𝑄 (mm/s)	𝐻hf (kOe)	D𝐻hf (kOe)	A (%)	Component identification	(A)/[B] site occupancy
γ-Fe2O3; Bare	16	1; 2; 3	0.39; 0.33; 0.34	—; —; 0.84	499; 438; —	28; 129; —	52; 44; 4	SR [B]; SR (A); FR	0.85
γ-Fe2O3; 5% OA	14	1; 2; 3; 4	0.35; 0.30; 0.38; 0.27	—; —; —; 0.79	483; 427; —; —	39; 105; —; —	18; 21; 60; 1	SR [B]; SR (A); IR; FR	1.17
γ-Fe2O3; 10% OA	8	1; 2; 3; 4	0.39; 0.31; 0.35; 0.27	—; —; —; 0.75	482; 425; —; —	41; 112; —; —	22; 25; 51; 2	SR [B]; SR (A); IR; FR	1.14
γ-Fe2O3; 20% OA	7	1; 2; 3; 4	0.40; 0.29; 0.33; 0.35	—; —; —; 0.80	482; 420; —; —	42; 122; —; —	22; 30; 47; 2	SR [B]; SR (A); IR; FR	1.36
*Bulk γ-Fe2O3		1; 2	0.41; 0.27	—; —	499; 488	—; —		[B]; (A)	0.60

Isomer shifts, δ: referenced to metallic iron at RT (error: ±0.03 mm/s), Δ𝐸_𝑄: quadrupole splitting (error: ±0.05 mm/s), 𝐻_hf: average magnetic hyperfine field (error: ±3 kOe), D𝐻_hf: FWHM of magnetic hyperfine field distribution, A: absorption area (error: ±5%), SR: slow relaxation, FR: fast relaxation, IR: intermediate relaxation, (A): tetrahedral spinel site, and [B]: octahedral spinel site.
*Source [24].